Step 1: Quit out of Mail if it's running

Step 2: Enable your desired logging options

Make sure Mail is not running, and - logged in as the user in question with the account in Mail that you want to work with -
use the Terminal to issue the desired 'defaults' options, for example:

defaults write com.apple.mail LogMessageTransferTimes -bool true

Step 3: Run Apple mail with the following command (via the Terminal)

Again, make sure Mail is not running, and - logged in as the user in question with the account in Mail that you want to work with -
use the Terminal to issue the following - modifying your.server.here appropriately, eg: mail.mycompany.com